The present invention relates primarily to a dispenser for gel deodorants or other semisolid products, and particularly to the head of a deodorant dispenser and methods of making the head and otherwise treating porous media so as to have properties desired in a semisolid product dispenser.
Deodorants and antiperspirants (hereinafter jointly referred to as deodorants) are typically applied to the skin of the underarm from some form of dispenser. Years ago aerosol cans were commonly employed to dispense deodorants. Deodorants in solid form have become popular. The solid deodorant is held in a body that has a piston. A cap is removed from the body, and the piston is activated to force the solid deodorant upwardly until the top portion is exposed. The top portion can then be rubbed onto the underarm skin.
Most recently, clear, gel deodorants have been proposed. Other semisolid forms of deodorant, such as creams or soft sticks, have also been suggested. One of the benefits of such semisolid deodorants is that they are less expensive to manufacture, because the fluid nature of the semisolid deodorant allows it to be pumped and easily loaded into a dispenser as part of the manufacturing step. One of the difficulties with dispensing a gel or other semisolid is that there must be a surface onto which the semisolid deodorant is applied, which is then brought into contact with the underarm. One prior art gel deodorant dispenser used a type of a grate. Gel was forced upwardly from within a body holding the gel through holes in the grate. The gel stayed on top of this grate and was then wiped onto the skin of the underarm. The grate was rigid, and was formed by injection molding plastic into a mold. The holes were formed by core pins within the mold.
Another proposal was to take a woven screen material and insert mold the woven screen material into a frame, thus forming a head. However, because the woven screen material was not rigid, it was proposed to include supports within the head to force the screen material to take on a dome shape so that it could contact the skin of the underarm. Several problems have been encountered with this proposal. First, the supports inherently block some of the openings in the screen, and the gel comes out unevenly across the screen. However, if no supports are used, and the screen collapses, all of the gel under the screen will come out, causing an overdose.
Second, the opening size of the screen plays conflicting roles. If the opening size is too large, the gel material will flow out if the dispenser is tipped on its side. On the other hand, if the opening size is too small, the gel material has to be put under such pressure when it is forced through the screen that the gel structure is compromised. For example, the liquid portion of the gel may disassociate from solid portions, or oil and water emulsions of other semisolid deodorants may break. In addition, when a semisolid deodorant is over pressurized, it continues to ooze out even though the user no longer activates the piston, and in fact may have set the dispenser aside after using it. When the user comes back, the deodorant has come through the screen and dried on top of the screen.
Another problem with woven screen material is that it is difficult to provide openings consistently sized any smaller than 400 square microns (20 microns by 20 microns) when making a weave. It is nearly impossible to make an opening smaller than 5 microns by 5 microns using a woven screen. If a media with an opening of 2 microns or less is desired, a porous membrane usually has to be used. Thus, if the semisolid deodorant material has a low viscosity, it may not be possible to make a normal woven screen with a pore size that will prevent the material from leaking out.
Another problem with the use of a woven screen is that the percent open area of a screen gets smaller and smaller as the pore size is reduced. The strands or fibers making the screen must be large enough to give integrity to the screen. As they are placed closer and closer to one another to reduce the pore size, the ratio of open area to area blocked by the fibers is reduced. The problem with a low percentage open area is that the amount of material that can be forced through the screen is reduced as the percent open area is decreased.
Another problem with a woven screen material is that if it is stretched while being manufactured as part of the dispensing head, especially around the edges when a rounded shape piece of media is used, the openings are not uniform. More deodorant could come out of the larger openings than the openings in the middle of the piece of media.
Besides the porous media itself, there are other difficulties in making a head for a semisolid product dispenser. Because the semisolid product is a gel or some other fluid material, all of the passageways between where it is stored and where it is dispensed must be fluid tight so that the product does not leak out under pressure. If parts of the dispenser are made out of an inexpensive thermoplastic material such as polypropylene, it is difficult to form leak-free joints between the parts, as polypropylene does not normally form strong bonds between parts. At times, ultrasonically welded parts only look like they are bonded because polypropylene is soft and the parts deform instead of welding together. Later, when under pressure, the parts come apart. Such a joint would be unacceptable in a semisolid product dispenser, as the dispenser head could come apart when the product was forced through it, causing the gel deodorant or other semisolid product to gush out and make a mess in the hands of the user as the joint came apart. Other thermoplastic materials could be used, but their cost would be a significant disadvantage where the dispenser is made in mass quantities and only used once before being thrown away.
The foregoing problems, as well as other difficulties encountered during development of a semisolid product dispenser head, have been overcome by the present invention. A porous material made from an extrusion of strands of polymer has been found which provides desired properties in making a head for a semisolid product dispenser. Also, it has been discovered that the opening size and shapes of the openings of a porous media can be improved for use in a semisolid product dispenser by crushing the media between two hard surfaces, such as parts of a mold tool. Further, an ultrasonic weld joint has been developed which can be used to securely join inexpensive polypropylene.
In a first aspect, the invention is a method of making a head for a semisolid product dispenser comprising the steps of providing a piece of porous media having a desired shape with a perimeter and openings through the media in the area inside of the perimeter; compressing at least the portion of the media inside of the perimeter between two parts of a hard tool so as to crush the media, thereby reducing the size of the openings; and affixing the porous media to a head frame to form the semisolid product dispenser head.
In a second aspect, the invention is the method of making a head for a semisolid product dispenser comprising the steps of providing a piece of porous media made of multiple layers of extruded strands wherein the strands are generally coplanar and parallel to one another within each layer and the strands in one layer are non-parallel to strands in an adjoining layer and bonded to the strands in the adjoining layer at crossover points between the strands; and insert molding the piece of porous media with a thermoplastic material into a head frame to thereby produce a head for a semisolid product dispenser.
In a third aspect, the invention is an improved porous media where the porous media has multiple layers of extruded strands of polymer with the strands in each layer being generally coplanar and parallel to one another, the direction of the strands in one layer being non-parallel to the strands in an adjoining layer, the strands being bonded to the strands in the adjoining layer at crossover points between the strands, and the media having openings through the media defined by spaces between the strands in one layer superimposed over spaces between strands in the adjoining layer, improved in that the average size of the openings through the media are reduced by crushing the strands of one layer against the strands of an adjoining layer, thereby flattening the strands and reducing the size of the spaces between the strands.
In a fourth aspect, the invention is an improved dispenser for dispensing a semisolid product where the dispenser includes a hollow body containing a semisolid product and a piston to force the semisolid product out of the hollow body through a porous media affixed to a head secured on the body, improved in that the porous media comprises multiple layers of extruded strands of polymer wherein the strands in each layer are generally coplanar and parallel to one another, the direction of the strands in one layer being non-parallel to the strands in an adjoining layer, the strands being bonded to the strands in the adjoining layer at crossover points between the strands, and the media having openings through the media defined by spaces between the strands in one layer superimposed over spaces between strands in the adjoining layer.
In a fifth aspect, the invention is a method of reducing the pore size of a porous media comprising the steps of providing a porous media comprising multiple layers of extruded strands of polymer wherein the strands in each layer are generally coplanar and parallel to one another, the direction of the strands in one layer being non-parallel to the strands in an adjoining layer, the strands being bonded to the strands in the adjoining layer at crossover points between the strands, and the media having openings through the media defined by spaces between the strands in one layer superimposed over spaces between strands in the adjoining layer; and compressing the media between two opposing hard surfaces so as to flatten the individual strands, thus making the strands wider in a direction perpendicular to the hard surfaces, thereby reducing the size of the openings between the strands.
In a sixth aspect, the invention is a method of making a semisolid product dispenser comprising the steps of providing a head frame with a top end and a sidewall depending from the top end; providing a body member that mates with the head frame, defining a deodorant holding and distribution space between the top end and the body member; providing mating ultrasonic weld joint surfaces on the head frame and the body member that provide a weld joint and a positive stop; and ultrasonically welding the body member and head frame together.
In a seventh aspect, the invention is a semisolid product dispenser comprising a head frame having a top end and a sidewall depending from the top end, the top end having a porous media attached thereto; a body member having an outer wall inside of the sidewall, the head top end and body member having a semisolid product holding and distribution space between them; and the body member outer wall being ultrasonically welded to the head frame to provide a leak-free joint so that all semisolid product in said body member may be forced out of said holding and distribution space through the porous media.
In an eighth aspect, the invention is a method of reducing the pore size of a porous media comprising the steps of providing a porous media having a first average thickness with openings therethrough creating a first average pore size; and compressing the media between opposing surfaces on a core and a cavity of a mold tool so as to reduce the average thickness of the media and to reduce the size of the openings through the media to create a second average pore size smaller than the first average pore size.
In a ninth aspect, the invention is a method of making a head for a semisolid deodorant dispenser comprising the steps of providing a piece of generally flat porous media having a perimeter; forming the porous media into a dome shape; and attaching the perimeter to a head frame having a central opening therethrough such that the dome shape of the media is retained, the media and the dome shape formed being rigid enough such that even though the media is supported only by its edges, the dome does not collapse when the head is pressed against underarm skin with normal user force sufficient to spread deodorant forced through the media across the skin.
In a tenth aspect, the invention is a deodorant dispenser comprising a body holding a semisolid deodorant and a dispensing head, the dispensing head having a frame with a central opening therethrough and a porous media shaped in the form of a dome convex of the rest of the head, the media having a perimeter which is attached to the head frame, the dome extending over the central opening, and the media being sufficiently rigid when in the dome shape such that the dome does not collapse when the head is pressed against underarm skin with normal user force sufficient to spread semisolid deodorant forced through the media across the skin.